To determine whether reperfused myocardial infarction (RMI) induces PTM of the delta-subunit of the mitochondrial metabolic enzyme ATP synthase (ATP/delta) in the ischemic zone (IZ) and whether this can be reversed by the angiotensin II type 1 receptor (AT(1)R) blocker valsartan, we applied a pharmaco-proteomics approach in canine RMI hearts with or without valsartan pretreatment. Using the 2-DE technique, we identified differential regional expression of ATP/delta in the IZ compared to the non-ischemic zone (NIZ), with an approximately 2-fold increase in the IZ that was normalized by valsartan. Furthermore in the IZ, RMI triggered S-nitrosylation of cysteine-100, nitration of the two tyrosines 88 and 225, and hydroxylation of lysine-182 in ATP/delta followed by its myristoylation. Importantly, valsartan abolished these modifications of ATP/delta in the IZ, triggered phosphorylation of serine-76 in both the IZ and NIZ, and decreased necrosis, apoptosis, left ventricular dysfunction and remodeling. Thus, AT(1)R-blocker-induced cardioprotection during RMI is associated with phosphorylation of ATP/delta and inhibition of nitric oxide-related chemical modifications such as S-nitrosylation, nitration and hydroxylation. Targeting specific PTMs during RMI, such as those of ATP/delta with AT(1)R blockade, might be a potentially powerful novel therapeutic approach. However, the identification of S-nitrosylation was putative and requires MS/MS verification.